1. Field of the Invention
The present invention relates to a ski binding.
2. Description of Prior Art
Ski bindings have been developed which automatically release the boot of a skier when excessive forces are exterted on the leg, which are strong enough to cause serious lesions to the leg. Generally, the release of this type of binding is accomplished mechanically against the bias of one or more springs which bias the binding against release of the boot. The boot is released when the force exerted on the leg is greater than the bias of the springs. This bias of the springs is adjustable by the skier.
Because the release depends only upon the value of the bias of the springs, these bindings have serious shortcomings. These shortcomings arise because serious lesions to the leg are a function of both the magnitude of the force and the duration of the force. Thus, the leg may be injured by a force below the threshold of the springs which has a long duration because these bindings do not take the duration of the force exerted on the leg into account. Furthermore, the leg of a skier can sustain a violent force if the force is sufficiently brief in duration. The value of the force the leg of a skier can withstand decreases as a function of the time during which this force is applied. This function is substantially hyperbolic.
In order to take into account the duration of the force as well as the magnitude of the force, bindings having electric release circuits have been developed. These bindings generally comprise a maintenance element for the boot which is controlled by an electromagnet. The electromagnet is connected to an electronic circuit having force constraint gauges. The gauges sense various forces acting on the leg and send this input to the electronic circuits.
Although bindings using an electric release circuit offer the advantage of being able to take into account the duration of the force discussed above, they also suffer from certain disadvantages. First, the forces acting on the leg cannot be detected in a reliable manner. Although force gauges may accurately detect forces on one or more test bodies under laboratory test conditions, and consequently produce good results in the laboratory, the force gauges do not function properly during skiing. This occurs because the force gauges can become loose or disengage from the binding due to bad adhesion, or as a result of shocks, or as a result of the influence of low temperatures. Second, the electric circuits needed for these bindings must constantly be maintained under voltage. This requires the use of electric power batteries, which quickly run down. This is a serious disadvantage. Furthermore, because the release is susceptible to such problems as the rapidity of response, aging, and reliability, the electric circuits are also adversely affected. Finally, the use of electronic releases alone is not normally acceptable to skiers for two additional reasons. In electronic releases there is a direct transmission of the shocks to the leg of the skier, which is uncomfortable and there is the danger of a possible malfunction.